Refrigerating apparatus



May 17, 1938. T. s. WETTER I I 2,

REFRIGERATING APPARATUS Filed May 14, 1937 wlT NEsfiEs INVENTOR 7H, 4 W 1 10171625 8. weifer' BY H z M M, d W

ATTORNEY$ Patented May 17, 1938 UNITED STATES PATENT OFFICE REFRIGERATING APPARATUS Thomas S. Wetter, New York, N. Y.

Application May 14, 1937, Serial No. 142,565

6 Claims.

proved refrigerating apparatus whereby a more uniform temperature may be maintained in the space or object to be refrigerated. I

i In the ordinary automatic refrigerating system,

control mechanism usually consists of a pressure control operated by a variation in the evaporator pressure or a thermostat operated by a variation intemperature of the space or product to be cooled. With either type of mechanism there is usually a temperature variation of several degrees due to a great extent to the fact that during the period when the refrigerating machine is shut down the evaporation of the refrigerant continues and builds up the pressure in the evaporator to a point above the normal operating pressure and before refrigeration is obtained it is necessary for the refrigerating apparatus to reduce the evaporator pressure to the normal operating pressure.

It is a particular object of the invention to overcome the undesirable relatively large fluctuation in temperature resulting from refrigerating apparatus of the type heretofore employed and to provide improved control mechanism for maintaining a more uniform temperature in the space or object to be refrigerated.

For a fuller understanding of the invention, reference should be had to the accompanying drawing showing a diagrammatic illustration of one form of refrigerating apparatus embodying my invention.

My invention may be used in association with any type of conventionaTrefrigerating apparatus having a compressor, condenser and evaporator. In the accompanying drawing one form of re- 40 frigerating apparatus is shown consisting of compressor l operated by an electric motor 2 and having inlet and outlet ducts 3 and 4, respectively. The inlet duct 3 is provided with a valve 5 which opens on the intake stroke of the compressor and closes on the compression stroke, while the outlet duct 4 is provided with a similar but oppositely operating valve 6 which closes on the intake stroke and opens on the compression stroke. The refrigerating fluid accordingly is drawn into the compressor through duct 3 and forced outwardly through duct 4, whence it is fed to the condenser where the heat is extracted from the fluid. From the condenser. I the refrigerant passes through pipe 8, through expansion valve I, into evaporator III which is of the coil type.

The expansion valve 9 is of the conventional thermostatically controlled type, being connected by a tube or duct H to a thermobulb or jacket l2 surrounding outlet pipe it which leads from the evaporator coil 10.; g g I .The apparatus heretoforedescribed is" one of the conventional types of refrigerating apparatus and is merely intended as illustrative of the type of apparatus to which my invention maybe applied. In associationwith the refrigerating ap paratus, I employ improved control mechanism which effectively prevents too great'afiuctuation in the temperature of the space to be refrigerated. In carrying out myinve'ntion I provide means having relatively great volurnetric capacity between the outlet of the evaporator and the compressor, thereby forming a space of reduced pressure which can immediately reduce the pressure inthe evaporator to the desired operating pressure whenthe refrigerating machine is set into operation.

7 Thus the pipe it is connected to a suction tank which in turn has connection through pipe 5 with the intake 3 of the compressor. The tank 05 is of relatively large capacity relative to the capacity of the evaporator iii and is preferably maintained at a pressure lower than the desired operating pressure of the evaporator. In this way when the refrigerating apparatus is set into operation the tank 05 can immediately reduce the pressure of the evaporator without the pressure in the tank being greatly affected, and accordingly the operating time of the refrigerating apparatus is not wasted by having the compressor first reduce the pressure of the evaporator to normal operating pressure.

So that the pressure in the line I4 may be readily observed, I preferably place a gauge at some convenient place in the line, as indicated at 40.

In the line l4 between the evaporator I0 and the tank I5 I provide a pressure regulating valve ll of the suction pressure type and thermostatically controlled valve is which automatically opens when the temperature of the space or object to be refrigerated rises to a predetermined point. The pressure regulating valve I8 is of the well known suction pressure or back pressure type and is intended to maintain the pressure in the evaporator at the desired operating pressure even though the pressure in the tank l5 should be considerably below that level. The pressure at which the valve I8 is set depends upon the refrigerant employed and also upon the temperature which it is desired to maintain in the space to be refrigerated and also the expected or average heat infiltration in that space. Thus, for example, where Freon is employed as the refrigerant, and where it is desired to maintain the temperature of a space at 58 F., and it is determined from the average heat loss that the operating temperature of the evaporator l should be approximately 48 F., the pressure regulating valve I8 is adjusted so as to maintain a gauge pressure in the line I4 of approximately 45 lbs.

The thermostatically controlled-valve I9 is operated by a solenoid 20 which is connected by leads 2| and 22 to one side of a source of current supply and by lead 23 to contact 24 of thermostatic switch 25. The switch 25 is provided with a thermostatically operated movable contact 26 having an elongated head 21 and which has connection through lead 28 to the other side of the source (if current supply. The valve 19 is normally closed so as to shut off the connection between the evaporator l0 and suction tank l5, but when a predetermined temperature is reached the contact 26 automatically engages contact 24 closing the circuit of solenoid 20 and opening the valve I9. Since as previously stated the pressure tank I is maintained at a level below the desired operating pressure of the evaporator Hi the pressure of the evaporator will be immediately reduced to the desired amount when the valve I9 is open. Pressure regulator valve l3 prevents a reduction of the pressure in the evaporator below the desired level.

At times the'heat infiltration is greater than expected, with the result that the operation of the refrigerating machine at the pressure determined by the regulating valve 18 is not sufllcient to overcome the heat infiltration and the temperature will continue to rise. To meet this contingency I provide a by-pass in the form of pipe 30 connected at one end to the pipe l4 between the evaporator and the regulating valve l8 and at its other end to the pipe I6. The pipe 30 is controlled by a thermostatic valve 3| operated by solenoid 32. The solenoid 32 is connected by leads 33 and 22 to one side of the source of current supply and by lead 34 to fixed contact 35 of the thermostatically operated switch 25. The contact 35 is positioned so as to be engaged by contact 26 upon the continued rise in tempera ture in the space or object to be refrigerated above the temperature at which the contact 24 is operated.

The pipe 30 has no pressure regulating valve, such as the valve i8 disposed therein, and ac-- cordingly when solenoid 32 causes valve 3| to open, the pressure in pipe l4 and in the evaporator I0 is reduced below the pressure which is permitted by the pressure regulating valve I8 upon the opening of valve Hi. The result is that upon the opening of valve 3| the pressure and temperature of the refrigerant in the evaporator and accordingly the temperature of the evaporator decreases, causing a more rapid cooling of the space which should be sufficient to overcome the additional heat infiltration.

Tank I5 is maintained at the desired reduced pressure by means of compressor I. When the pressure in the tank l5 rises above the desired amount the compressor is caused to operate to reduce the pressure. This may be accomplished by means of a conventional type of diaphragm or similar pressure operated switch as shown at 36 which is controlled and operated by the pressure in tank IS. The switch is connected by lead 31 to one side of a source of current supply and by lead 33 to the compressor operating motor 2. The compressor operating motor is also connected by lead 39 to the opposite side of the source of current supply. When Freon is employed as the refrigerant and it is desired to maintain the evaporator coils at a temperature of approximately 48 F. and the pressure is set at 45 lbs. gauge pressure, I have found that satisfactory results are obtained by maintaining the pressure in tank I5 at between and 25 lbs. gauge pressure. Thus the switch 36 may be ad- Justed so as to cause the compressor motor 2 to operate when the pressure rises to 25 lbs. and to shut the motor oif after the pressure has been reduced to 10 lbs. I

, As an illustration of the manner in which my apparatus may be operated, let us assume that Freon is employed as the refrigerant and that it is desired to maintain the space refrigerated at approximately 58 F. Let it be further assumed that the heat infiltration and other factors are such that the evaporator coil I0 should have an operating temperature of approximately 48 F. in order to maintain the room at the desired temperature. The thermostatic switch 25 is then adjusted so as to cause the closing of contact 24 at 58 and the closing of contact 35 at 58*. If greater temperature fluctuations are permissible the thermostatic switch may be adjusted so as to cause the closing of the contacts at higher temperatures such as 58 and 59. The settings of the switch will of course depend upon the degree of uniformity of temperature which it is desired to maintain. The pressure regulating valve I8 is adjusted so as to maintain a gauge pressure of 45 lbs. in the line l4 and evaporator I0, and the switch 36 is adjusted so that the gauge pressure of tank IE will be maintained between 10 and 25 lbs. as previously described.

When the device is thus adjusted and the temperature in the space to be refrigerated rises to 581 s contact 24 will be closed causing solenoid 20 to open valve l9. Since the capacity of tank I5 is large relative to the capacity of evaporator I0 and since the pressure is maintained at between 10 and 25 lbs., the opening of valve ll results in an immediate reduction of the gauge pressure of evaporator 10 to 45 lbs., thereby effectively and immediately eliminating any fluid pressure that is built up in the evaporator due to the evaporation of the refrigerant while the refrigerating apparatus was inoperative. Accordingly there is no delay occasioned by a slow reduction of the pressure in the evaporator by the compressor and the apparatus may operate almost immediately to refrigerate the space after the opening of valve l9.

Since the apparatus has been adjusted or regulated so that the temperature of evaporator Ill when operating at 45 lbs. gauge pressure is sufficient to overcome the normal heat infiltration, the opening of valve I9 is usually suflicient to cause the gradual reduction in temperature in the space to be refrigerated. However, under certain conditions the heat infiltration may be greater than usual, with the result that evaporator l0 may not be able to overcome it when operating at 45 lbs. gauge pressure, with the result that the temperature in the space to be refrigerated continues to rise until contact is closed, causing solenoid 32 to open valve 3|, thereby by-passing pressure regulator II. The result of this is to reduce the pressure in the evaporator below that permitted by pressure regulating valve l8, the pressure in the evaporator being reduced to 35 lbs. or less depending upon the pressure existing in tank l5 at that time.

The reduction in the pressure in the evaporatorcauses a greater cooling of the refrigerant, which under most conditions should be able to overcome the additional heat infiltration causing a gradual reduction in the temperature of the space to be refrigerated.

Instead of using just a single by-pass 30 as shown, a plurality of by-passes may be employed which are controlled by valves operating at successively higher temperatures and each by-pass causing a further reduction in the pressure in evaporator Hi. It will also be appreciated that the temperatures and pressures mentioned herein are merely illustrative of one form of setting and where different types of refrigerants are employed and difierent temperatures are desired different adjustments will also be required. Once the nature and operation of my device is understood, however, anyone skilled in the art will be able to adjust the thermostatically controlled switch 25, the pressure regulating valve l8, and the pressure operated switch 36 to produce the desired results.

It will be seen from the herein described and illustrated embodiment of my invention that I have provided an improved refrigerating appara tus, particularly control mechanism, whereby undesirable fluctuations in temperature in the refrigerated space can be eliminated and whereby a high degree of uniformity of temperature can be obtained. It will be understood that many modifications may be made in the illustrated and described embodiment of my invention such as combining the control mechanism with other types of refrigerating apparatus and by employing a plurality of by-passes as above described. Also instead of employing a suction tank l enlarged or extended piping may be employed.

I claim:

1. The combination with refrigerating apparatus having a compressor and an evaporator, of means having relatively large volumetric capacity as compared to the capacity of the evaporator and having connection with the outlet oi. the evaporator and with the intake of the compressor, thereby providing a relatively large space of reduced pressure communicating with the outlet of the evaporator, a pressure regulating valve in the connection between said means and the evaporator for regulating the minimum pressure in the evaporator, an automatically controlled valve for opening and closing said connection, a by-pass around said regulating valve, and an automatically operating control valve for the bypass.

2. The combination with refrigerating apparatus having a compressor and an evaporator, of means having relatively large volumetric capacity as compared to the capacity of the evaporator and having connection with the outlet of the evaporator and with the intake of the compressor, thereby providing a relatively large space of reduced pressure communicating with the outlet of the evaporator, a pressure regulating valve in the connection between said means and the evaporator for regulating the minimum pressure in the evaporator, a control valve in said connection having a thermostatic control for 'opening the valve at a predetermined temperature, a

by-pass around the pressure regulating valve,

and a control valve for the by-pass having a thermostatic control for opening the second-mentioned valve at a predetermined higher temperature.

3. The combination with refrigerating apparatus having a compressor and an evaporator, of means having relatively large volumetric capacity as compared to the capacity of the evaporator and having communication with the intake of the compressor so as to provide a relatively large space of reduced pressure, a plurality of separate ducts each having communication at one end with the outlet of the evaporator and at the other end with said means having a large volumetric.

tus having a compressor and an evaporator, of a tank having connection with the intake of the compressor and with the outlet of the evaporator, a pressure regulating valve in the connection between the evaporator and the tank for regulating the pressure in the evaporator, a control valve having a thermostatic control for opening the valve at a predetermined temperature, a by-pass around the regulating valve, and a control valve for the by-pass having a thermostatic control for opening the second-mentioned valve at a predetermined higher temperature than the first-mentioned valve. v

5. The combination with refrigerating apparatus having a compressor, condenser and evaporator, of a tank having a relatively large volumetric capacity as compared to the capacity of the evaporator and having connection with the intake of the compressor so as to provide a relatively large space of reduced pressure, a plurality of ducts having communication at one end with the outlet of the evaporator and at the other end with the said tank, a pressure regulating valve in one of said ducts for regulating the pressure in the evaporator, and control valves for said ducts having thermostatic controls for opening the valve at predetermined temperatures, the control valve in the duct which is provided with a pressure regulating valve opening at a lower temperature than another of said valves.

6. In refrigerating apparatus, an evaporator, and means for reducing the pressure in the evaporator, said means including a pressure regulating valve for regulating the pressure in the evaporator at a predetermined level when a predetermined temperature is reached and means for rendering the pressure regulating valve ineffective when a higher predetermined temperature is reached.

THOMAS S. WE'ITER. 

